Communication satellites provide communication support for a wide region. Typically the supported region is an area on the surface of the earth that lies within the beam of a satellite that is directed towards the earth. The region can be relatively stationary such as when the communication satellite is a geostationary satellite. The region may vary over time such as when the communication satellite is a low earth orbit (LEO) satellite. Some systems may require numerous satellites each having multiple beams. Other communication systems may use a single satellite covering a wide coverage area in a single beam. For example, a communication system may use a single communication satellite having a beam that covers a region that includes the entire continental United States.
The reliability of a satellite is of utmost concern because communication satellites often are used to provide critical communication links. The remote nature of a communication satellite combined with the extended period of time needed to put a replacement satellite into space makes the satellite a single point whose failure can bring down communication channels for an extended period of time. To alleviate the single point failure nature of a communication satellite, communication system designers often provide an in-orbit spare satellite in order to maintain the communication channels in case the operating satellite fails. The spare satellite is not normally used for communications, but is used to provide system redundancy. If the operational satellite should fail, the communications are switched to the in-orbit spare in order to maintain communications. The failed satellite can then be repaired or decommissioned. Another in-orbit spare can then be placed into space to provide a redundant communication satellite.
In satellite communication systems where a single communication satellite can support a region as large as the continental United States, the in-orbit spare represents a large system cost that provides a disproportionately small benefit. It would be advantageous to reduce the system burden of a dormant in-orbit spare.